A wet etching process is utilized to etch material from target locations on a semiconductor substrate during fabrication of integrated circuits (ICs). The success of the wet etching process requires an etching chemistry that includes chemical compositions suitable for selectively removing one material while substantially not removing another material. Therefore, various chemical compositions have been developed for removal of specific classes of materials from substrates in semiconductor wafer technologies.
Silicon nitride is commonly used as a cap layer, spacer layer or hard mask layer in semiconductor devices. Generally, a silicon nitride layer on the semiconductor substrate is selectively etched and removed by soaking the substrate in a hot phosphoric acid bath for a period of time. Nevertheless, in the etching process, particles such as silica precipitates may be generated and then accumulated in the bath so as to reduce etching performance and shorten bath age. Besides, cross-contamination among semiconductor substrates may occur, and thus a post-cleaning process, which results in extra manufacturing cost, is needed to clean each of the semiconductor substrates. Given the above, it remains desirable to provide a process without the post-cleaning process to save the manufacturing cost.